Triangulum Galaxy (M33) - 2023-10-25 - Circular Light Pollution Gradient
This image represents the end of my quest to overcome bright sky limits upon wide band photography by the sheer brute force of collecting a grunch of signal.
I have concluded that the circular gradient in this image is the result of light pollution in a Bortle 7 sky. The image is produced from a stack of 20s x 144 subs.
I found online examples of similar gradients that were attributed to a bright moon in the sky, so it seems reasonable that a bright Bortle 7 sky, and the nearby Washington DC light dome could cause a similar effect.
Improper calibration as a cause was eliminated by reprocessing without flat or dark calibration frames, and the gradient persisted. I tried another processing run with only 8 subs, and found that the signal was reduced. This seems to indicate that the problem increases with signal, and the image will only get worse with more subs collected.
The M33 and M78 luminance images that I captured on Nov 13th at a dark sky site did not have the circular gradient. This suggests that only images taken in a light polluted sky are the only ones that suffer from the gradient.
Finding that the ill effects of a bright sky are causing the circular gradient, I revisited light pollution filters as a possible cure, thinking that there is something better on the market now than when I last looked into it several years ago.
No matter what I try with background extraction, neither DBE nor ABE can take care of this gradient. Conventional wisdom for solving this problem seems to be to add a gasoline filter to one's vehicle, and then to drive out to a dark site.
Triangulum Galaxy (M33) - 2023-10-25 - Circular Light Pollution Gradient
This image represents the end of my quest to overcome bright sky limits upon wide band photography by the sheer brute force of collecting a grunch of signal.
I have concluded that the circular gradient in this image is the result of light pollution in a Bortle 7 sky. The image is produced from a stack of 20s x 144 subs.
I found online examples of similar gradients that were attributed to a bright moon in the sky, so it seems reasonable that a bright Bortle 7 sky, and the nearby Washington DC light dome could cause a similar effect.
Improper calibration as a cause was eliminated by reprocessing without flat or dark calibration frames, and the gradient persisted. I tried another processing run with only 8 subs, and found that the signal was reduced. This seems to indicate that the problem increases with signal, and the image will only get worse with more subs collected.
The M33 and M78 luminance images that I captured on Nov 13th at a dark sky site did not have the circular gradient. This suggests that only images taken in a light polluted sky are the only ones that suffer from the gradient.
Finding that the ill effects of a bright sky are causing the circular gradient, I revisited light pollution filters as a possible cure, thinking that there is something better on the market now than when I last looked into it several years ago.
No matter what I try with background extraction, neither DBE nor ABE can take care of this gradient. Conventional wisdom for solving this problem seems to be to add a gasoline filter to one's vehicle, and then to drive out to a dark site.